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Electric field and electrolytes

  1. Jul 22, 2013 #1
    Let me assume, that I have an arbitrary electric field. Is there any way to determine what happens to this electric field if it is appolied to a charge in let me say water with natrium chloride in it? I guess there is some kind of response to the electric field by the ions, so that it will just "die out", as the electrolytes will screen it. Is there an equation that would confirm this idea?
  2. jcsd
  3. Jul 22, 2013 #2
    It seems that the response of the water molecules is more important than that of the ions.
    The relative permittivity of water at room temperature is about 80, this means that if you place a charge near or in water, the electric field will be reduced by a factor of 80 because the polar water molecules line up with the field.
    If you put a voltage on 2 plates in the water (low enough so you won't get electrolysis) the field will be the same for water as for vacuum or air, because you get 80 times more charges on the plates immersed in water, until the field strength is equal to a vacuum capacitor.

    The permittivity of water depends on temperature. If the temperature is higher, the faster movement of the water molecules will make it harder to align with the field.

    Now if you add some salt, this will cause water molecules close to the ions to align with the field with the ions, and this will decrease the alignment with the external field.

    this is described here http://arxiv.org/abs/1208.5169
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